Chinese researchers propose new explanation for ultra-long gamma-ray burst

BEIJING, Feb. 20 (Xinhua) -- Chinese researchers have developed a novel model to explain the origin of an ultra-long gamma-ray burst (GRB), challenging the conventional understanding of these violent cosmic events.

Gamma-ray bursts are among the most violent explosive phenomena in the universe, typically lasting from milliseconds to a few minutes. However, the GRB 250702B event, which occurred on July 2, 2025, exhibited extraordinary properties that have sparked intense debate within the astrophysics community.

A research team from the Chinese Academy of Sciences Institute of High Energy Physics conducted a comprehensive analysis of satellite observational data, including Insight-HXMT and GECAM. They examined the data from 30 days around the burst and discovered that the gamma-ray emission lasted an unprecedented 29 hours, shattering previous duration records.

The team also identified distinctive time variabilities in the accompanying X-ray radiation. Based on these findings, they proposed a new model stating that the progenitor star of this gamma-ray burst was a supergiant with a mass far exceeding that of the Sun, as reported in their recent research article published in the Astrophysical Journal Letters.

Unlike the progenitors of ordinary gamma-ray bursts, the collapse of supergiant stars can extend over dozens of days. When the supergiant exhausts its nuclear fuel, its core first collapses to form a black hole, which rapidly accretes the inner material of the supergiant star, producing relativistic jets traveling at nearly the speed of light. This is the source of the gamma-ray burst.

During the subsequent accretion process, slightly slower jets were generated, emitting X-ray radiation. ■